There is no reason you can't use the Wiimote as a pointing device. It has been done and a quick google would show you how to do it.
However I think it is impractical for most PC users, we tend to sit at a desk with a smaller screen to play our games on PC. Our console friends however tend to sit back from their substantially larger TV. Making more room for the kind of Motion Control we are seeing from the consoles these days.
Since when does the Wii use touch screen? When did I miss this? Doesn't the Wii just utilize motion control and an infrared sensor? Touch screens have been around for years and they are just awful for gaming, I mean you literally have to cover the screen with your hand and it would be rather imprecise on most size monitors. See barside game touch stations as reference.
Yea, i'm with fisch. First the Wii doesn't use a touchscreen, and secondly, your hands and fingers tend to not be clear (if they are, consult your doctor, lol) which means you tend to block what you're trying to mess with. Not to mention the accuracy of a mouse and keyboard far exceed fingers.